There has developed around rubber latex a substantial industry for producing such articles as condoms, rubber gloves, surgical supplies, balloons, bathing caps and countless other articles. The articles are generally produced by dipping glass, porcelain or metal mandrels into natural rubber latex baths and subsequently coagulating and curing the thin film of latex, which adheres to the mandrel. Thicker films are obtained by repeating the dipping, coagulating and curing operations as desired. The films are stripped from the mandrels and may optionally be further cured at elevated temperatures.
Normally a condom is made of strong, fine rubber, fine animal membrane or a synthetic polymer such as polyurethane. Of necessity, in order to provide an acceptable level of tactile stimulation to the wearer, the condom must be quite thin. In general, it is elastically fitted to the male organ and during coitus remains stretch and taut.
The traditional methods of manufacturing a contraceptive, prophylactic or condom involve the so-called straight dipping or dip and dry techniques wherein a phallic shaped mandrel of predetermined size is, optionally coated with a coagulating agent, and dipped into a bath containing natural rubber latex or a solution of synthetic polymer such as polyurethane. The mandrel when dipped may be stationary or rotating about its longitudinal axis. The mandrel is then removed from the bath, dried and cured. This process can be repeated several times until a condom of the desired thickness properties are achieved. During dipping, the mandrel is immersed to a depth sufficient to yield the finished condom of desired length plus an additional distance to allow for rolling the sheath on itself for several turns in order to form a ring at the open end of the condom. Following a final cure, the formed condom may be coated with an anti-tack material such as talc, micro-porous solid particles, lubricants, slip agents, spermicides, deodorants, etc., prior to removal from the mandrel.
After completion of the dipping, ring-forming, curing and optional coating steps, the condom is removed from the mandrel, and optionally subjected to additional drying, further curing, and quality testing. Prior to packaging, the condoms are quality tested and rolled to form a cup-shaped elastic ring of predetermined size and circumference. At this point, additional lubricants, spermicides, bactericides, etc., may also be added to the condom. In this form, the condom is easily mountable for use during sexual intercourse by unrolling onto the penis.
Currently, condoms are manufactured under the Trojan Brand™ name, as well as other names with ribbed features. These ribbed features are typically made by dipping a mandrel with an etched surface into a latex bath. Latex deposits on the surface of the dipped mandrel to form the basic condom shape, while the latex that deposits in the etchings leaves behind a ribbed feature on the finished condom exterior.
However through trial and error, it has been determined that for a condom having a typical mid-point thickness of 0.075 mm, the maximum height that can be accomplished by the above mentioned technique is only about 0.1 mm or less. Such height usually does not provide much sensation to the condom user or partner. Attempting to make features with a greater height, through deeper etching of the condom mandrel, results in the formation of unacceptable weak spots on the condom. Broader (wider) raised patterns are also problematic. Latex tends to form a uniform coating in a broadly etched section of the mandrel rather than filling the void. This results in the pattern being lost once the condom is removed from the mandrel.
By using a grooved mandrel on which condoms are manufactured by a dip molding process, it is possible to produce condoms with ribs that are claimed to heighten stimulation during coitus. However, the ribs on such condoms produced by the known method are not effectively positioned or lack sufficient structural rigidity to produce effective clitoral and labial stimulation, and the production of pronounced ribbing by shaping of the mandrel weakens the structural integrity of the condom which is plainly unacceptable.
U.S. Pat. No. 6,182,661 to Solanki et al discloses a method for producing condom having monolithic projections to promote stimulation of clitoris. Specifically, Solanki et al. apply the projections between dips to a pre-deposited latex sheath. However such method substantially slows down the production speed, and the ability to manufacture a wider array of projections onto condoms is limited. Therefore, there remains a need for an efficient method of producing such condoms having projections greater than 0.1 mm in height to produce stimulation,